1. Field of the Invention
This present invention relates to displaying both plano-stereoscopic images and autostereoscopic images. More specifically, the present design relates to eliminating the conflict of cues that occurs at the vertical edges of the screen surround when objects having negative parallax values are partially occluded by the surround.
2. Description of the Related Art
Plano-stereoscopic images are images made up of a left and a right perspective image and are most often viewed using an individual selection device, or eyewear. Autostereoscopic images are defined as stereoscopic images that can be viewed without the use of an individual selection device as image selection takes place at the screen or display surface. While plano-stereoscopic imaging is predominantly discussed herein, a worker skilled in the art will be able to understand the changes that can be implemented to apply these teachings to autostereoscopic imaging.
Plano-stereoscopic or autostereoscopic images may be projected on a screen or viewed on a display monitor. Frequently such images may also be displayed as hard-copy using photomechanical reproduction. In the case of plano-stereoscopic images, the anaglyph is the frequently used viewing modality, where an anaglyph comprises images in contrasting colors that appear three-dimensional when superimposed over one another and viewed through eyewear using complimentary colors. In the case of autostereoscopic still images, a hardcopy can be achieved using an overlaid lenticular screen.
In order to understand the concept of vertical surround correction, one first needs to understand the concept of image parallax in a plano-stereoscopic or autostereoscopic display. Referring to FIGS. 1A through 1D, display surface 101 in these figures includes demonstrations made up of points with various parallax values to be viewed by an observer whose left eye is 104 and right eye is 105. The lines of sight of the eyes—which, for the purposes of this discussion, correspond to the optical axis of the eyes' lenses—are, for the left and right eyes, 102 and 103 respectively. The distance between left and right eyes 104 and 105 is known as the interpupillary distance, given by line 106.
In FIG. 1A, the left and right image points on display surface 101 are given by point 107 that is made up of superimposed left and right image points. These left and right image points correspond or overlap and this condition is known as “zero parallax.” Such an image point will appear at the plane of the display surface 101, and the eyes tend to converge inwardly to fuse point 107 so that lines of sight 102 and 103 cross at point 107.
Zero-parallax points appear at the plane of the screen (FIG. 1A), positive-parallax points appear behind the plane of the screen (FIG. 1B), and negative-parallax points appear in front of the screen (FIG. 1C). Beyond certain values the image becomes uncomfortable to view (FIG. 1D), or because of system constraints undesirable artifacts appear which contribute to difficulty in viewing the stereoscopic image. The concept of the breakdown of accommodation and convergence is an important one for stereoscopic displays and has an impact on the problem addressed here. In the real world, the eyes will both focus (or accommodate) and converge on objects in space in synchrony. Such focusing is a habitual or learned response, because the neurological pathways for accommodation and for convergence are separate. When looking at stereoscopic displays, the eyes will remain focused at the plane of the display, but convergence varies for various points dependent upon parallax values. This can produce stress or discomfort or what people sometimes call “eyestrain.”
In the case of the display shown in FIG. 2A, object 205 (represented by 205L and 205R in the left and right halves of the stereo pair respectively) has negative parallax. Object 206 (represented by 206L and 206R in the left and right halves of the stereo pair respectively), has positive parallax. Note that portions of object 205 (205 is meant to represent a complete rectangle) are cut off by the left vertical edges of the screen surround 203. In such a case the eye-brain will perceive that the image is trying to come off-screen because of the stereoscopic or parallax cue. However, the eye-brain also perceives a conflict of cues because the screen surround, or that portion of the stereo window at 203, also provides an important depth clue, namely one of interposition, tells the observer that the object must be behind the plane of the screen. In other words, a near object (element 205, having negative parallax) seems to be blocked by something that is farther away (the screen surround at zero parallax). This confusing condition is called a “conflict of cues,” and is to be avoided. To some people the result is perceived as a blur, to others it's merely uncomfortable, and to others the image does not seem to be coming off the screen as was intended, but gets pushed back into the screen. This imaging artifact never occurs in the visual world so people have no ready way to articulate what is being seen.
The present design seeks to cure the problem of the screen surround cue conflicts and thereby increase the enjoyment of perceiving a stereoscopic image. It would be advantageous to offer a design that can address parallax or stereoscopic cue conflicts in both large and small screen environments, particularly a design that offers benefits over that previously available.